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Publication numberUS4622438 A
Publication typeGrant
Application numberUS 06/674,827
Publication dateNov 11, 1986
Filing dateNov 26, 1984
Priority dateNov 29, 1983
Fee statusPaid
Also published asDE3483353D1, EP0144072A2, EP0144072A3, EP0144072B1
Publication number06674827, 674827, US 4622438 A, US 4622438A, US-A-4622438, US4622438 A, US4622438A
InventorsTakafumi Shimizu, Ichiro Tomizawa
Original AssigneeFujitsu Limited
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Subscriber line radio concentration system with automatic response for a loop back test
US 4622438 A
Abstract
In a subscriber line radio concentration system for concentrating a plurality of subscriber terminal stations through radio channels to a master station, at least one of the subscriber terminal stations comprises an automatic response equipment. The automatic response equipment can automatically respond to a continuous ringing signal from the master station, thereby enabling a loop back test to be carried out automatically without the necessity of the attendance at the subscriber station of maintenance or other personnel.
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Claims(11)
We claim:
1. A subscriber line radio concentration system for concentrating a plurality of subscriber terminal stations through radio channels to a master station, at least one of said subscriber terminal stations comprising an automatic response equipment;
said automatic response equipment comprising:
a ringing signal rectifying circuit for rectifying a ringing signal transmitted from said master station through a subscriber line to said subscriber terminal station,
a charging circuit for boosting the voltage rectified by said ringing signal rectifying circuit;
a voltage-stabilizing circuit for providing a constant voltage when the output voltage from said charging circuit exceeds a predetermined value;
an oscillating circuit for generating a predetermined signal when said constant voltage is generated from said voltage-stabilizing circuit; and
a quasi OFF HOOK setting circuit for conducting said predetermined signal from said oscillating circuit through said subscriber line to said master station.
2. A subscriber line concentration system as set forth in claim 1, wherein said voltage-stabilizing circuit provides said constant voltage only when said ringing signal is continuous for a predetermined period.
3. A subscriber line concentration system as set forth in claim 1, wherein said predetermined signal generated by said oscillating circuit is an audio signal.
4. A subscriber line concentration system as set forth in claim 1, further comprising a relay circuit driven by said constant voltage, said quasi OFF HOOK setting circuit being adapted to conduct said predetermined signal in response to the output of said relay circuit.
5. A subscriber line concentration system as set forth in claim 4, wherein said constant voltage from said voltage-stabilizing circuit is adapted to be applied to said relay circuit and to said oscillating circuit as a power supply voltage.
6. A subscriber line concentration system as set forth in claim 1, wherein said quasi OFF HOOK setting circuit comprises coils for magnetically coupling said predetermined signal with said subscriber line, and a relay contact for forming a loop between said oscillating circuit and said master station when said relay circuit is activated by said constant voltage applied from said voltage-stabilizing circuit.
7. A subscriber line concentration system as set forth in claim 1, wherein said oscillating circuit comprises odd number of inverters connected in series, said inverters being adapted to receive said constant voltage as their power supply voltage.
8. A subscriber line concentration system as set forth in claim 1, wherein at least one of said subscriber terminal stations comprises: terminal equipment including an antenna duplexer, transmitter/receiver equipment connected to said antenna duplexer, and control equipment connected to said transmitter/receiver equipment; and a telephone set;
said telephone set and said automatic response equipment being connected through a cable subscriber line to said terminal equipment.
9. A subscriber line concentration system as set forth in claim 1, wherein at least one of said subscriber terminal stations comprises: terminal equipment including an antenna duplexer, transmitter/receiver equipment connected to said antenna duplexer, and control equipment connected to said transmitter/receiver equipment; and a telephone set;
said telephone set and said automatic response equipment being connected through a radio channel to said terminal equipment.
10. A subscriber line concentration system as set forth in claim 1, wherein said master station comprises a control equipment including a test call unit for carrying out a loop back test, a plurality of transmitter/receiver equipments connected to said control equipment, and an antenna duplexer connected to said transmitter/receiver equipments, said control equipment being connected via wires to said transmitter/receiver equipments.
11. A subscriber line concentration system as set forth in claim 1, wherein said master station comprises a control equipment including a test call unit for carrying out a loop back test, a plurality of transmitter/receiver equipments connected to said control equipment, and an antenna duplexer connected to said transmitter/receiver equipments, said control equipment being connected via radio channels to said transmitter/receiver equipments.
Description
BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a subscriber line radio concentration system. More particularly, it relates to a subscriber line radio concentration system (in other words, a multiple access radiotelephone system) having an automatic response unit suitable for a loop back test pertaining to a transmission test of access lines from a master station (servicing switching center) to a user (subscriber) terminal equipment.

(2) Description of the Related Art

In the multiple access radiotelephone system, both the master station and the subscriber terminal station cannot be constantly supervised by maintenance personnel. Therefore, to determine whether or not the communication channel between the master station and the subscriber terminal station is defective, it is desirable that a loop back test be carried out automatically.

In the conventional loop back test, however, it is necessary for someone such as a maintenance engineer to be in attendance at the called subscriber terminal station. Such personal attendance is necessary because, when a call is effected from a master station to a subscriber terminal station, the connection of the communication channel between the calling master station and the called subscriber terminal station is acknowledged only when an individual, in response to a ringing tone at the called subscriber terminal station, lifts the handset of the telephone set and responds to the call. Therefore, conventionally, a fully automatic loop back test cannot be carried out.

SUMMARY OF THE INVENTION

In view of the above-mentioned problem, an object of the present invention is to provide a subscriber line radio concentration system which can automatically carry out a loop back test from a master station to a subscriber terminal station.

To attain the above object, there is provided a subscriber line radio concentration system for concentrating a plurality of subscriber terminal stations through radio channels to a master station, wherein at least one of the subscriber terminal stations comprises an automatic response equipment. The automatic response equipment comprises: a ringing signal rectifying circuit for rectifying a ringing signal transmitted from the master station through a subscriber line to the subscriber terminal station; a charging circuit for boosting the voltage rectified by the ringing signal rectifying circuit; a voltage-stabilizing circuit for providing a constant voltage when the output voltage from the charging circuit exceeds a predetermined value; an oscillating circuit for generating a predetermined signal when the constant voltage is generated from the voltage-stabilizing circuit; and a quasi OFF HOOK setting circuit for conducting the predetermined signal from the oscillating circuit through the subscriber line to the master station.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and features of the present invention will be more apparent from the following description of the preferred embodiment with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram illustrating a multiple access radiotelephone system, according to an embodiment of the present invention;

FIG. 2 is a block diagram illustrating one of the subscriber terminal stations shown in FIG. 1;

FIG. 3 is a block diagram illustrating an automatic response equipment in the subscriber terminal station shown in FIG. 2;

FIGS. 4A through 4F are waveform diagrams illustrating the voltages at various points in the automatic response equipment shown in FIG. 3; and

FIG. 5 is a circuit diagram illustrating the automatic response equipment in detail.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a multiple access radiotelephone system according to an embodiment of the present invention. In FIG. 1, 1 designates exchange equipment; 2 a master station; and 3l through 3m a plurality of subscriber terminal stations. The subscriber terminal stations 31 through 3m are remote from the master station 2. For example, the subscriber terminal station 3l is separated from the master station 2 by a distance of, for example, 300 km. Accordingly, the subscriber terminal stations 3l through 3m are associated with the master station 2 via duplex radio channels CH1 through CHn. The suffix m of the subscriber terminal stations 3l through 3m represents a number of stations, for example, 120. The suffix n of the radio channels CH1 through CHn usually represents a number smaller than that represented by m. For example, eight radio channels CH1 through CH8 are provided. Calls are made via idle channels.

The master station 2 consists of a control equipment (CONT) 21, transmitter/receiver equipment (T/R) 22l through 22n, and an antenna duplex equipment (DUP) 2. The antenna duplex equipment 23 is connected to a nondirectional antenna 24.

Each of the subscriber terminal stations 3i (i=1, 2, 3, . . . , or m) consists of a terminal equipment (TE) 31i, a telephone set 32i, and an automatic response equipment 33i which is provided according to the present invention. The terminal equipment (TE) 32i is connected to a directional antenna 34i. The telephone equipment 32i and the automatic response unit 33i are connected through a subscriber line 35i to the terminal equipment (TE) 31i.

The control equipment 21 controls the whole system. In particular, it acts to specify one of the duplex channels CH1 through CHn and one of the subscriber terminal stations 3l through 3m. The control equipment 21 includes a test call unit 211 for carrying out a loop back test between the selected station of the subscriber terminal stations 3l through 3m and the master station 2.

When the control equipment 21 specifies one of the subscriber terminal stations 3l through 3m and one of the channels CH1 through CHn , and when the test call unit 211 is driven in such a manner that an examination mode is set, the master station calls the specified subscriber terminal station, for example, 3l, through the specified channel, for example, CH1, by sending a continuous ringing signal. The continuous ringing signal is thus provided on, for example, the subscriber line 351, and this ringing signal on the subscriber line 351 generates a continuous ringing tone at the telephone set 321.

Conventionally, the connection between the telephone equipment 321 in the subscriber terminal equipment 31 and the control equipment in the master station 2 is acknowledged by lifting the handset of the telephone set 321 in response to the continuous ringing tone. Therefore, if there is no-one present in the vicinity of the telephone set 321, the connection test cannot be performed.

Conversely, according to the present invention, the continuous ringing signal on the subscriber line 351 is applied also to the automatic response equipment 331. The automatic response equipment 331 then automatically generates an audio signal which is returned back through the subscriber line 351 to the master station 2, as later described in more detail. Thus, the loop back test can be carried out fully automatically and without the necessity for attendance by maintenance or other personnel.

FIG. 2 is a block diagram illustrating in more detail one of the subscriber terminal stations 3l through 3m. In FIG. 2, the terminal equipment (TE) 311 in the subscriber terminal station 3l includes an antenna duplexer (DUP) 36, a transmitter/receiver equipment (T/R) 37, and a control equipment (CONT) 38.

Instead of providing the telephone set 321 and the automatic response equipment (ARE) 331 within the subscriber terminal station 3l, these units may be located remote from the terminal equipment 311. In this case, the subscriber line 351 may be a long-distance cable or may be a wireless radio channel.

FIG. 3 is a block diagram illustrating the automatic response equipment (ARE) 331 in more detail. In FIG. 3, the automatic response equipment (ARE) 331 includes a ringing signal rectifying circuit (REC) 301 for rectifying the ringing signal transmitted from the master station 2 to the subscriber line 351, a charging circuit (CHA) 302 for charging the voltage rectified by the ringing signal rectifying circuit 301, a voltage-stabilizing circuit (STAB) 303 for providing a constant voltage V1 when the output voltage from the charging circuit 302 exceeds a predetermined voltage V0 , a relay circuit (RLY) 304 driven by the above-mentioned constant voltage V1 output from the voltage-stabilizing circuit 303, an oscillating circuit (OSC) 305 for generating a signal having a predetermined frequency f0, and a quasi OFF HOOK setting circuit (OFH) 306 for transferring the signal from the oscillating circuit 306 to the subscriber line 351 when the relay circuit (RLY) 304 is activated.

FIGS. 4A through 4E are waveform diagrams illustrating the voltage at respective points A, B, C, D, E, and F in the automatic response equipment 331 shown in FIG. 3.

FIG. 4A shows the waveform of the continuous ringing signal CRNG supplied from the master station 2 to the subscriber line 351. The peak-to-peak voltage is about 100 V. In the loop back test mode, the continuous ringing signal is transmitted instead of the intermittent ringing signal transmitted in a usual call. After rectifying the continuous ringing signal CRNG by the rectifying circuit 301, the output thereof is boosted by the charging circuit (CHA) 302, resulting in the waveform as shown in FIG. 4B. In FIG. 4B, the output voltage of the charging circuit 302 reaches the reference voltage V0 at a time t1. The voltage stabilizing circuit (STAB) 303 then provides the constant voltage V1 for a predetermined period td from the time t1. In response to the constant voltage V1, the relay circuit 304 is activated for that period td as shown in FIG. 4D. Also, by the constant voltage V1, the oscillation circuit 305 begins to generate the signal having the frequency f0 as shown in FIG. 4E. The frequency f0 preferably may be an audio frequency. In response to the operation of the relay circuit (RLY) 304, the quasi OFF HOOK setting circuit (OFH) 306 forms a quasi OFF HOOK circuit, which is identical to the state of lifting up of the handset of the telephone set. Thus, the signal having the frequency f0 is transferred, during the period td, from the oscillating circuit (OSC) 305 through the quasi OFF HOOK setting circuit 306 to the subscriber line 351, as shown in FIG. 4F.

Once the connection is established between the master station 2 and the subscriber terminal station 31 through the quasi OFF HOOK setting circuit 306, the test call unit (TC) 211 in the control equipment 21 (in FIG. 1) stops the transfer of the continuous ringing signal CRNG at the time t1. Therefore, the charging circuit (CHA) 302 begins to discharge from the time t1, so that its output voltage gradually decreases as shown in FIG. 4B. When the output voltage of the voltage stabilizing circuit 303 turns to zero volts at a time t2, as shown in FIG. 4C, the relay circuit (RLY) 304 is released from its activated state and the connection between the oscillating circuit 305 and the subscriber line 351 is cut in the quasi OFF HOOK circuit 306. Thus, the connection test between the master station 2 and the subscriber terminal station 3l can be automatically carried out without the attendance of any personnel.

It should be noted that the automatic response equipment 331 has another advantage in that it does not need any specific power supply unit such as an AC power supply, since it utilizes the rectified output of the continuous ringing signal CRNG as a power supply voltage.

FIG. 5 is a circuit diagram illustrating the automatic response equipment 331 in more detail.

In FIG. 5, TMI through TM7 are terminals. The terminal TM2 is connected to a first ground G connected to the earth. The ringing signal rectifying circuit 301 is formed by varistor diodes BD1 through BD3 for protecting lines l1 and l2 against a surge current applied thereto, resistors R1 and R2 having small resistances of, for example, 5 through 10 ohms, for protecting a relay contact rl, coupling capacitors C1 and C2, and a diode bridge consisting of diodes D1 through D4 for obtaining a full-wave rectified current.

The charging circuit 302 is formed by resistors R3 through R5 and capacitors C3 through C5. The time constant for charging is determined by the resistances of the resistors R3 and R4 and the capacitances of the capacitors C3 through C5. The resistor R5 is provided for determining the discharge time constant. By appropriately setting these resistances and capacitances, the output voltage at the terminal TM4 will not reach the predetermined voltage V0 unless the continuous ringing signal CRNG is applied to the terminals TM1 and TM3. That is, even when an intermittent ringing signal is applied to the terminals TM1 and TM3, the charges in the capacitors C3 through C5 are discharged through the resistor R5 so that the voltage at the terminal TM4 does not reach the voltage V0.

The voltage stabilizing circuit 303 consists of resistors R6 and R7, a Zener diode ZD1, a thyristor THY including a PNP transistor T1 and an NPN transistor T2, and a voltage regulator Re. When the voltage at the terminal TM4 is lower than the predetermined voltage V0, the thyristor THY is in an off state. When the voltage at the terminal TM4 reaches the voltage V0, the Zener diode ZD1 conducts a current so that the base current of the transistor T1 is drawn from the base of the transistor T1 to the Zener diode ZD1, resulting in an on state of the thyristor THY. The voltage regulator Re provides the constant voltage V1 when the thyristor THY is in an on state.

By the constant voltage V1, the relay circuit RL is activated so that the relay contact rl is closed. Also, the constant voltage V1 is applied to the oscillating circuit 305. E is a second ground connected to the ground line in the automatic response equipment 331.

The oscillating circuit 305 includes three inverters INV1 through INV3, resistors R8 and R9, and a capacitor C6. When the INV1, INV2, and INV3 connected in series receive the constant voltage V1, the oscillating circuit 305 generates the signal having the frequency f0 at the terminal TM7.

The quasi OFF HOOK setting circuit 306 includes the relay contact rl which is opened or closed in response to the output of the relay circuit 304, and coils CL which are magnetically coupled to the oscillating signal from the oscillating circuit 305. Thus, when the relay contact rl is closed, the oscillating signal is supplied through the lines l1 and l2 and through the terminals TM1 and TM3 to the terminal equipment (TE) 311 (FIG. 2). As a result, a loop is formed between the automatic response equipment (ARE) 331 and the control equipment 21 in the master station 2.

Although the above description mentions only the subscriber terminal station 31l, the explanation therein may be also applied to the other subscriber terminal stations 312 through 31m.

The present invention is not restricted to the above-mentioned embodiments, since various changes and modifications are possible within the scope of the invention. For example, the automatic response equipment 33i and the telephone set 32i (i=1, 2, . . . , or m) may be assembled into a single body.

Further, between the terminal equipment 31i and the telephone set 32i or the automatic response equipment 33i, other transit trunks may be provided. The important feature of this invention is that the automatic response equipment 33i is provided at the final stage of the communication line.

Still further, instead of assembling the control equipment 211 in the main station 2, the control equipment 211 may be connected via radio channels to the transmitter/receiver equipments (T/R) 22l through 22n.

Still further, the continuous ringing signal CRNG may be applied from outside of the exchange equipment 1.

From the foregoing description, it will be apparent that, according to the present invention, in a subscriber line radio concentration system, a loop back test from a master station to a subscriber terminal station can be automatically carried out without the attendance of any personnel at the subscriber terminal station. In particular, for a public telephone set provided at a place so remote from the master station that it is extremely inconvenient to dispatch maintenance personnel to that location, the automatic response equipment, when provided in the public telephone box, makes the loop back test easy.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4560842 *Apr 4, 1983Dec 24, 1985The General Electric Company, P.L.C.Telecommunication system loop-back unit
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5898921 *Jan 13, 1995Apr 27, 1999Nokia Telecommunications OyMonitoring of the operation of a subscriber unit
US6088588 *Mar 25, 1997Jul 11, 2000Nortel Networks CorporationMethod and wireless terminal for monitoring communications and providing network with terminal operation information
US6169883Mar 6, 1997Jan 2, 2001Nokia Telecommunications OyRemote test of a subscriber connection in a system implementing a wireless subscriber connection
US6381473 *Jun 12, 1998Apr 30, 2002Radio Communication Systems Ltd.Distributed antenna for personal communication system
US6744853Jan 21, 2000Jun 1, 2004Oakdene LimitedTesting of telephone lines
US7072648 *Jan 2, 2001Jul 4, 2006Nec Infrontia CorporationFault monitoring method for commodity management radio communicating apparatus, storage medium for storing fault monitoring program for commodity management radio apparatus and fault monitoring program
US20010007818 *Jan 2, 2001Jul 12, 2001Yoshiaki IchikawaFault monitoring method for commodity management radio communicating apparatus, storage medium for storing fault monitoring program for commodity management radio apparatus and fault monitoring program
EP0837615A2 *Oct 16, 1997Apr 22, 1998AT&T WIRELESS SERVICES, INC.Method and apparatus for testing cellular services in a first location from a second location remote from the first location
EP0837615A3 *Oct 16, 1997Jul 21, 1999AT&T WIRELESS SERVICES, INC.Method and apparatus for testing cellular services in a first location from a second location remote from the first location
WO1997033446A1 *Mar 6, 1997Sep 12, 1997Nokia Telecommunications OyRemote test of a wireless subscriber connection
WO2000044155A1 *Jan 20, 2000Jul 27, 2000Oakdene LimitedThe testing of telephone lines
Classifications
U.S. Classification455/425, 379/22.01, 379/333, 379/22, 455/423
International ClassificationH04M3/24, H04M3/26, H04M3/30, H04B7/26, H04W24/00
Cooperative ClassificationH04M3/301, H04M3/24, H04W24/00
European ClassificationH04W24/00, H04M3/30C, H04M3/24
Legal Events
DateCodeEventDescription
Nov 26, 1984ASAssignment
Owner name: FUJITSU LIMITED 1015, KAMIKOKANAKA, NAKAHARA-KU, K
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:SHIMIZU, TAKAFUMI;TOMIZAWA, ICHIRO;REEL/FRAME:004338/0860
Effective date: 19841116
Owner name: FUJITSU LIMITED,JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SHIMIZU, TAKAFUMI;TOMIZAWA, ICHIRO;REEL/FRAME:004338/0860
Effective date: 19841116
Apr 12, 1990FPAYFee payment
Year of fee payment: 4
Apr 25, 1994FPAYFee payment
Year of fee payment: 8
Apr 27, 1998FPAYFee payment
Year of fee payment: 12